What is the ruling of propagating and spreading Kufr [disbelief] ideas and ideologies?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

Whoever propagates or spreads Kufr [disbelief] ideas and ideologies, like slandering and defaming religion, or propagating that the Islamic Law is not suitable to rule with, or calls to secularism, or mocks the Prophet and so forth, and spreads all this among the people, then if the person who does this is originally a Muslim, he becomes a non-Muslim by doing so even if he was just joking as Allaah Says (what means): {And if you ask them, they will surely say, “We were only conversing and playing.” Say, “Is it Allaah and His verses and His Messenger that you were mocking?” Make no excuse; you have disbelieved [i.e. rejected faith] after your belief.}[Quran 9:65-66].

Therefore, if it is confirmed that what this person calls to is propagating and spreading Kufr [disbelief] ideas and ideologies, then it is an obligation to inform the ruler about him so that the ruling of an apostate would be applied to him and protect people from his harm.

We ask Allaah to enable people to repent and accept their repentance, and guide them to the straight path.

Allaah Knows best.